1. Field of the Invention
The present invention relates to a flow control device for controlling a flow amount of a fluid flowing through a passage. Particularly, the invention is suitably employed as a flow control device for controlling the flow amount of hot water flowing from a hot water supply source to a heating heat exchanger.
2. Description of Related Art
As a flow control device for controlling the flow amount of hot water flowing from a hot water supply source to a heating heat exchanger in a hot water circuit, there has been known, for example, the flow control device disclosed in JP-A5-248558, which will be described below with reference to FIGS. 27 and 28.
As shown in FIGS. 27 and 28, in a hot water circuit 1, there are disposed a water-cooled engine 2 serving as a hot water supply source, a mechanical water pump 3 operated while interlocking with the engine 2, a heater core 4 as a heat exchanger for heating air to be blown out into the passenger compartment of a vehicle, and a motor pump 5 being operated when electric power is supplied from a battery (not shown) thereto. Further, in the hot water circuit 1, there is disposed a flow control valve 6 for adjusting the flow amount of hot water flowing from the engine 2 to the heater core 4. The numeral 100 denotes a radiator.
The flow control valve 6 includes a valve housing 101 constituting a hot water passage in the hot water circuit 1 and a solenoid portion 102 fixed to the valve housing 101. The valve housing 101 is provided with a first inlet pipe 103 and a first outlet pipe 104 both constituting a hot water passage from the engine 2 to the heater core 4, a second inlet pipe 105 and a second outlet pipe 106 both constituting a second hot water passage from the heater core 4 to the engine 2, and a bypass pipe 107 constituting a bypass passage for bypassing hot water which has entered the second inlet pipe 105 directly to the first outlet pipe 104.
A shaft 108 passes through each interior of the valve housing 101 and the solenoid portion 102. Valve elements 111 and 112 are provided on the shaft 108. By the valve elements 111 and 112, when a first communication passage 109 for communicating between the first inlet pipe 103 and the first outlet pipe 104 is fully closed, a second communication passage 110 for communication between the second inlet pipe 105 and the bypass passage 107 is fully opened. On the other hand, when the first communication passage 109 is fully opened, the second communication passage 110 is fully closed.
When the solenoid portion 102 is energized and controlled by a control unit 113, the shaft 108 comes into the state shown in FIG. 27, in which the first communication passage 109 is fully closed and the second communication passage 110 is fully open. In this state, hot water of a high temperature is not supplied from the engine 2 to the heater core 4, so that the temperature of the heater core drops. On the other hand, when the solenoid portion 102 is deenergized by the control unit, the shaft 108 comes into the state shown in FIG. 28, in which the first communication passage 109 is fully opened and the second communication passage 110 is fully closed. In this state, hot water of a high temperature is supplied from the engine 2 to the heater core 4, so that the temperature of the heater core rises.
The control unit 113 determines a predetermined duty ratio according to a target temperature of the heater core 4 and, on the basis of the thus-determined duty ratio, performs a duty control so as to reciprocate the shaft 108 repeatedly between the position shown in FIG. 27 and the position shown in FIG. 28.
In the flow control device described above, the valve elements 111 and 112 collide with valve seats when the shaft 108 moves from the position shown in FIG. 27 to the position shown in FIG. 28 and also when the shaft 108 moves from the position shown in FIG. 28 to the position shown in FIG. 27, thereby causing a problem in that the valve colliding noise is generated.
Further, since the duty control is performed between the position (FIG. 28) in which the first communication passage 109 is fully opened and the position (FIG. 27) in which the passage 109 is fully closed, when the shaft 108 shifts from the position indicated in FIG. 28 to the position indicated in FIG. 27, the first communication passage 109 in which a large amount of hot water is flowing is suddenly closed fully, thereby causing a problem in that a water hammer noise is generated.
Moreover, since the duty control is performed between the position in which the first communication path 109 is fully opened and the position in which the passage 109 is fully closed, the variation in the temperature of the heater core 4 may increase unless the duty control cycle is shortened. If the cycle is shortened, the number of operations of the shaft 108 becomes larger, thereby causing a problem in that the durability deteriorates.